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Coax Impedance Calculator

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Coax Impedance Calculator | RF Transmission Designer
Results
Impedance (Zo)-
Propagation Delay-
Inductance-
Capacitance-

Input Parameters Specification

Conductor ID (d1) The baseline external mechanical boundary diameter profile thickness of the interior active signal wire core pin component.
Surface Shield ID (d2) The internal opening clearance diameter scale measured across the interior boundary face of the outer metal grounding jacket layer.

Practical Operational Examples

Example 1: Standard RG-58 Test Setup

• Conductor ID = 35.0 mil | Surface Shield ID = 116.0 mil
• Dielectric Constant = 2.30 (Solid Polyethylene)
• Output Impedance: ~47.4 Ω | Delay Parameter: ~0.129 ns/in

Example 2: Semirigid Foam Substrate Matrix

• Conductor ID = 20.0 mil | Surface Shield ID = 67.0 mil
• Dielectric Constant = 1.44 (Expanded Teflon)
• Output Inductance: ~6.14 nH/in | Capacitance Profile: ~1.17 pF/in

Coax Cross Section Theory
d1 Conductor ID Shield Inner ID (d2) Coax Radial Cross Section Dielectric Substrate (er) Characteristic Impedance Zo = 60 / sqrt(er) * ln(d2/d1) d2 = Shield Inner ID d1 = Conductor ID Bigger d2/d1 ratio increases impedance
Formulas
Zo = 60 / sqrt(er) * ln(d2 / d1)
Delay = 84.72 * 10^-3 * sqrt(er)
Inductance = 5.08 * ln(d2 / d1)   (expressed in nH/in)
Capacitance = 1.41 / ln(d2 / d1)   (expressed in pF/in)

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About this tool

Coax Impedance Calculator is a free online calculator tool. Use it to get instant, accurate results for your electronics calculations.